/*
	FreeRTOS.org V4.2.1 - Copyright (C) 2003-2007 Richard Barry.

	This file is part of the FreeRTOS.org distribution.

	FreeRTOS.org is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	FreeRTOS.org is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with FreeRTOS.org; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

	A special exception to the GPL can be applied should you wish to distribute
	a combined work that includes FreeRTOS.org, without being obliged to provide
	the source code for any proprietary components.  See the licensing section
	of http://www.FreeRTOS.org for full details of how and when the exception
	can be applied.

	***************************************************************************
	See http://www.FreeRTOS.org for documentation, latest information, license
	and contact details.  Please ensure to read the configuration and relevant
	port sections of the online documentation.

	Also see http://www.SafeRTOS.com for an IEC 61508 compliant version along
	with commercial development and support options.
	***************************************************************************
*/

/*
 * A sample implementation of pvPortMalloc() and vPortFree() that permits
 * allocated blocks to be freed, but does not combine adjacent free blocks
 * into a single larger block.
 *
 * See heap_1.c and heap_3.c for alternative implementations, and the memory
 * management pages of http://www.FreeRTOS.org for more information.
 */
#include <stdlib.h>

#include "FreeRTOS.h"
#include "task.h"

/* Setup the correct byte alignment mask for the defined byte alignment. */

#if portBYTE_ALIGNMENT == 8
#define heapBYTE_ALIGNMENT_MASK ( ( size_t ) 0x0007 )
#endif

#if portBYTE_ALIGNMENT == 4
#define heapBYTE_ALIGNMENT_MASK	( ( size_t ) 0x0003 )
#endif

#if portBYTE_ALIGNMENT == 2
#define heapBYTE_ALIGNMENT_MASK	( ( size_t ) 0x0001 )
#endif

#if portBYTE_ALIGNMENT == 1
#define heapBYTE_ALIGNMENT_MASK	( ( size_t ) 0x0000 )
#endif

#ifndef heapBYTE_ALIGNMENT_MASK
#error "Invalid portBYTE_ALIGNMENT definition"
#endif

/* Allocate the memory for the heap.  The struct is used to force byte
alignment without using any non-portable code. */
static struct xRTOS_HEAP
{
  unsigned portLONG ulDummy;
  unsigned portCHAR ucHeap[configTOTAL_HEAP_SIZE];
} xHeap;

/* Define the linked list structure.  This is used to link free blocks in order
of their size. */
typedef struct A_BLOCK_LINK
{
  struct A_BLOCK_LINK *pxNextFreeBlock;	/*<< The next free block in the list. */
  size_t xBlockSize;		/*<< The size of the free block. */
} xBlockLink;


static const unsigned portSHORT heapSTRUCT_SIZE =
  (sizeof (xBlockLink) + (sizeof (xBlockLink) % portBYTE_ALIGNMENT));
#define heapMINIMUM_BLOCK_SIZE	( ( size_t ) ( heapSTRUCT_SIZE * 2 ) )

/* Create a couple of list links to mark the start and end of the list. */
static xBlockLink xStart, xEnd;

/* STATIC FUNCTIONS ARE DEFINED AS MACROS TO MINIMIZE THE FUNCTION CALL DEPTH. */

/*
 * Insert a block into the list of free blocks - which is ordered by size of
 * the block.  Small blocks at the start of the list and large blocks at the end
 * of the list.
 */
#define prvInsertBlockIntoFreeList( pxBlockToInsert )								\
{																					\
xBlockLink *pxIterator;																\
size_t xBlockSize;																	\
																					\
	xBlockSize = pxBlockToInsert->xBlockSize;										\
																					\
	/* Iterate through the list until a block is found that has a larger size */	\
	/* than the block we are inserting. */											\
	for( pxIterator = &xStart; pxIterator->pxNextFreeBlock->xBlockSize < xBlockSize; pxIterator = pxIterator->pxNextFreeBlock )	\
	{																				\
		/* There is nothing to do here - just iterate to the correct position. */	\
	}																				\
																					\
	/* Update the list to include the block being inserted in the correct */		\
	/* position. */																	\
	pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock;					\
	pxIterator->pxNextFreeBlock = pxBlockToInsert;									\
}
/*-----------------------------------------------------------*/

#define prvHeapInit()																\
{																					\
xBlockLink *pxFirstFreeBlock;														\
																					\
	/* xStart is used to hold a pointer to the first item in the list of free */	\
	/* blocks.  The void cast is used to prevent compiler warnings. */				\
	xStart.pxNextFreeBlock = ( void * ) xHeap.ucHeap;								\
	xStart.xBlockSize = ( size_t ) 0;												\
																					\
	/* xEnd is used to mark the end of the list of free blocks. */					\
	xEnd.xBlockSize = configTOTAL_HEAP_SIZE;										\
	xEnd.pxNextFreeBlock = NULL;													\
																					\
	/* To start with there is a single free block that is sized to take up the		\
	entire heap space. */															\
	pxFirstFreeBlock = ( void * ) xHeap.ucHeap;										\
	pxFirstFreeBlock->xBlockSize = configTOTAL_HEAP_SIZE;							\
	pxFirstFreeBlock->pxNextFreeBlock = &xEnd;										\
}
/*-----------------------------------------------------------*/

void *
pvPortMalloc (size_t xWantedSize)
{
  xBlockLink *pxBlock, *pxPreviousBlock, *pxNewBlockLink;
  static portBASE_TYPE xHeapHasBeenInitialised = pdFALSE;
  void *pvReturn = NULL;

  vTaskSuspendAll ();
  {
    /* If this is the first call to malloc then the heap will require
       initialisation to setup the list of free blocks. */
    if (xHeapHasBeenInitialised == pdFALSE)
      {
	prvHeapInit ();
	xHeapHasBeenInitialised = pdTRUE;
      }

    /* The wanted size is increased so it can contain a xBlockLink
       structure in addition to the requested amount of bytes. */
    if (xWantedSize > 0)
      {
	xWantedSize += heapSTRUCT_SIZE;

	/* Ensure that blocks are always aligned to the required number of bytes. */
	if (xWantedSize & heapBYTE_ALIGNMENT_MASK)
	  {
	    /* Byte alignment required. */
	    xWantedSize +=
	      (portBYTE_ALIGNMENT - (xWantedSize & heapBYTE_ALIGNMENT_MASK));
	  }
      }

    if ((xWantedSize > 0) && (xWantedSize < configTOTAL_HEAP_SIZE))
      {
	/* Blocks are stored in byte order - traverse the list from the start
	   (smallest) block until one of adequate size is found. */
	pxPreviousBlock = &xStart;
	pxBlock = xStart.pxNextFreeBlock;
	while ((pxBlock->xBlockSize < xWantedSize)
	       && (pxBlock->pxNextFreeBlock))
	  {
	    pxPreviousBlock = pxBlock;
	    pxBlock = pxBlock->pxNextFreeBlock;
	  }

	/* If we found the end marker then a block of adequate size was not found. */
	if (pxBlock != &xEnd)
	  {
	    /* Return the memory space - jumping over the xBlockLink structure
	       at its start. */
	    pvReturn =
	      (void
	       *) (((unsigned portCHAR *) pxPreviousBlock->pxNextFreeBlock) +
		   heapSTRUCT_SIZE);

	    /* This block is being returned for use so must be taken our of the
	       list of free blocks. */
	    pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;

	    /* If the block is larger than required it can be split into two. */
	    if ((pxBlock->xBlockSize - xWantedSize) > heapMINIMUM_BLOCK_SIZE)
	      {
		/* This block is to be split into two.  Create a new block
		   following the number of bytes requested. The void cast is
		   used to prevent byte alignment warnings from the compiler. */
		pxNewBlockLink =
		  (void *) (((unsigned portCHAR *) pxBlock) + xWantedSize);

		/* Calculate the sizes of two blocks split from the single
		   block. */
		pxNewBlockLink->xBlockSize =
		  pxBlock->xBlockSize - xWantedSize;
		pxBlock->xBlockSize = xWantedSize;

		/* Insert the new block into the list of free blocks. */
		prvInsertBlockIntoFreeList ((pxNewBlockLink));
	      }
	  }
      }
  }
  xTaskResumeAll ();

  return pvReturn;
}

/*-----------------------------------------------------------*/

void
vPortFree (void *pv)
{
  unsigned portCHAR *puc = (unsigned portCHAR *) pv;
  xBlockLink *pxLink;

  if (pv)
    {
      /* The memory being freed will have an xBlockLink structure immediately
         before it. */
      puc -= heapSTRUCT_SIZE;

      /* This casting is to keep the compiler from issuing warnings. */
      pxLink = (void *) puc;

      vTaskSuspendAll ();
      {
	/* Add this block to the list of free blocks. */
	prvInsertBlockIntoFreeList (((xBlockLink *) pxLink));
      }
      xTaskResumeAll ();
    }
}

/*-----------------------------------------------------------*/
